The opportunity to utilize wireless features is ever increasing as cellular transceivers are being transformed into entertainment as well as communication platforms. One such cellular transceiver is a wireless feature included within wireless vehicle communication and networking services for a mobile vehicle. Another such cellular transceiver includes capabilities to receive satellite broadcasts such as, for example, Global Positioning System (GPS) signals and satellite radio signals.
Typically, wireless systems within mobile vehicles (e.g., telematics units) provide voice communication. These wireless systems have also been utilized to update systems within telematics units such as, for example, radio station presets. Recently, additions have included the ability to provide positioning information and extra entertainment via the use of satellite reception capabilities.
Cellular transceivers operate within communication systems, for example, a telematics unit within a mobile vehicle operating within a mobile vehicle communication system (MVCS). Cellular transceivers operating within communication systems can receive large amounts of electromagnetic traffic including, but not limited to, wireless communications, GPS signals, satellite signals, and the like.
Unfortunately, there are certain locations where GPS signals are not reliable. To improve location determinations within these areas, many GPS systems rely on dead reckoning (DR). The DR process combines satellite measurements with additional sources of location information such as inertial gyroscopes, accelerometers, compass information, and wheel speed sensors. For best DR performance, GPS satellite measurements must be augmented with additional speed and heading information. These data when combined can predict the absolute location of a vehicle (expressed as a latitude and longitude) when GPS measurements are either unreliable or unavailable. Accurate speed and heading information will reliably predict (for short periods of time) changes in vehicle velocity and the direction in which the vehicle is traveling. A need exists for improved accuracy in the information used to determine the telematics equipped vehicle's position for presentation to a user or service provider when GPS service is interrupted.
The present invention advances the state of the art in accurately determining a vehicle's geographic location.